1. Technical Field
The present invention relates to a manufacturing method and a manufacturing apparatus of optical material for optical goods such as a plastic lens.
2. Related Art
Traditionally, optical goods such as plastic lenses are manufactured by mixing a plurality of materials, injecting the mixture into a mold and polymerizing the materials within the mold. Since the polymerization is not sufficiently conducted according to the type of used materials, it is considered effective to conduct a preliminary reaction step for preliminarily reacting the materials before being injected into the mold.
In order to manufacture optical goods of a constant quality, the progress of the preliminary reaction is preferably controlled.
For instance, Document 1 (JP-A-2004-137481) discloses a preliminary reaction and deaerating processing that are conducted before a reacting composition is injected into a mold, where the progress of the reaction is detected by measuring a refractive index of a reacting composition. Specifically, an in-line refractometer is attached to a blend tank in which the preliminary reaction and the deaerating processing are conducted and a detector portion of the refractometer is always immersed in the reacting composition, so that the refractive index of the reacting composition is measured and monitored to control the progress of the blending operation.
In a manufacturing process of optical goods such as plastic lenses, the injecting operation of monomer (reacting composition) has come to be automated, where it is difficult to inject the monomer into the mold if the viscosity of the monomer is lower than a predetermined value. Manual injection allows injection of more viscous monomers than the monomers that can be injected by automated injection. However, it still is difficult to be injected into the mold when the viscosity of the monomer is lower than a predetermined value.
According to the progress management by measuring the refractive index as disclosed in the Document 1, the variation in quality of the final lenses can be restrained to a certain degree. However, since the viscosity is not recognized, it is likely that some trouble occurs when the monomer is injected into the mold. In other words, the progress management based on refractive index is not always effective for stable production in an actual mass production process.